Browsing by Author "Datta, Kasturi"

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Evidence for inhibitory interaction of hyaluronan binding protein 1 with S. pneumoniae hyaluronidase
(The American Society for Biochemistry and Molecular Biology, Inc., 2009) Yadav, Gitanjali; Prasad, Ramachandra L. A.; Jha, Babal Kant; Rai, Vivek; Bhakuni, Vinod; Datta, Kasturi
Bacterial hyaluronan lyase enzymes are the major virulence factors that enable greater microbial ingress by cleaving hyaluronan (HA) polymers present predominantly in extracellular space of vertebrates. Based on the premise that effective inhibitors may bind to and stabilize HA thereby protecting it from degradation, here we investigated inhibitory activity of human hyaluronan-binding protein 1 (HABP1) on bacterial hyaluronidase because it is highly specific to HA and localized on the cell surface. Biochemical characterization revealed that HABP1 is a competitive inhibitor of Streptococcus pneumoniae hyaluronate lyase (SpnHL) with an IC50 value of 22 uM. This is thus the first report of an endogenous protein inhibitor that may be used dur- ing natural antibacterial defense. Our findings also support a novel multipronged mechanism for the high efficacy of HABP1- mediated inhibition based on structural modeling of enzyme, substrate, and inhibitor. Evidence from docking simulations and contact interface interactions showed that the inherent charge asymmetry of HABP1 plays a key role in the inhibitory activity. This novel role of HABP1 may pave the way for peptide inhibitors as alternatives to synthetic chemicals in antibacterial research.
In vivo role of Candida albicans β-hexosaminidase (HEX1) in carbon scavenging
(John Wiley & Sons, 2015) Ruhela, Deepa; Kamthan, Mohan; Saha, Paramita; Majumdar, Subeer S.; Datta, Kasturi; Abdin, Malik Zainul; Datta, Asis
The capability to utilize of N-acetylglucosamine (GlcNAc) as a carbon source is an important virulence attribute of Candida albicans. But there is a lack of information about the in vivo source of GlcNAc for the pathogen within the host environment. Here, we have characterized the GlcNAc-inducible β-hexosaminidase gene (HEX1) of C. albicans showing a role in carbon scavenging. In contrast to earlier studies, we have reported HEX1 to be a nonessential gene as shown by homozygous trisomy test. Virulence study in the systemic mouse murine model showed that Δhex1 strain is significantly less virulent in comparison to the wild-type strain. Moreover, Δhex1 strain also showed a higher susceptibility to peritoneal macrophages. In an attempt to determine possible substrates of Hex1, hyaluronic acid (HA) was treated with purified Hex1 enzyme. A significant release of GlcNAc was observed by gas chromatography-mass spectrometry analysis analysis suggesting HA degradation. Interestingly, immunohistochemistry analysis showed significant accumulation of HA in the mice kidney infected with the wild-type strain of C. albicans. Northern blot analysis showed that C. albicans HEX1 is expressed during mice renal colonization. Thus, C. albicans can obtain GlcNAc during organ colonization by secreting Hex1 via degradation of host HA.